The present invention relates generally to the continuous separation of particulate matter from a flowing liquid by the use of a centrifugal field. More specifically the present invention relates to the use of spiral plates or vanes within the centrifuge bowl in cooperation with a suitable propulsion arrangement for self-driven rotation of the spiral vanes. In one embodiment of the present invention, the propulsion arrangement includes the use of jet nozzles. In other embodiments of the present invention, the specific shape and style of the spiral vanes are modified, including the embodiment of flat (planar) plates. Also, in these other embodiments, the styling of the cooperating components is modified, thereby providing different final assembly embodiments.
Since the use of spiral vanes in the preferred embodiment of the present invention is a design change to the prior art technology employing a cone-stack subassembly as the basis for particulate matter separation from the flowing liquid, a review of this cone-stack technology may be helpful in appreciating the differences between the present invention and the prior art and the benefits afforded by the present invention.
U.S. Pat. No. 5, 575,912, which issued Nov. 19, 1996 to Herman et al., discloses a bypass circuit centrifuge for separating particulate matter out of a circulating liquid. The construction of this centrifuge includes a hollow and generally cylindrical centrifuge bowl which is arranged in combination with a base plate so as to define a liquid flow chamber. A hollow center tube axially extends up through the base plate into the hollow interior of the centrifuge bowl. The bypass circuit centrifuge is designed so as to be assembled within a cover assembly and a pair of oppositely-disposed tangential flow nozzles in the base plate are used to spin the centrifuge within the cover so as to cause particles to separate out from the liquid. The interior of the centrifuge bowl includes a plurality of truncated cones which are arranged into a stacked array and are closely spaced so as to enhance the separation efficiency. The stacked array of truncated cones is sandwiched between a top plate positioned adjacent to the top portion of the centrifuge bowl and a bottom plate which is positioned closer to the base plate. The incoming liquid flow exits the center tube through a pair of oil inlets and from there flows through the top plate. The top plate in conjunction with ribs on the inside surface of the centrifuge bowl accelerate and direct this flow into the upper portion of the stacked array of truncated cones. As the flow passes radially inward through the channels created between adjacent cones, particle separation occurs. Upon reaching the inner diameter of the cones, the liquid continues to flow downwardly to the tangential flow nozzles.
U.S. Pat. No. 5,637,217, which issued Jun. 10, 1997 to Herman et al., is a continuation-in-part patent based upon U.S. Pat. No. 5,575,912. The U.S. Pat. No. 5,637,217 discloses a bypass circuit centrifuge for separating particulate matter out of a circulating liquid. The construction of this centrifuge includes a hollow and generally cylindrical centrifuge bowl which is arranged in combination with a base plate so as to define a liquid flow chamber. A hollow center tube axially extends up through the base plate into the hollow interior of the centrifuge bowl. The bypass circuit centrifuge is designed so as to be assembled within a cover assembly and a pair of oppositely-disposed tangential flow nozzles in the base plate are used to spin the centrifuge within the cover so as to cause particles to separate out from the liquid. The interior of the centrifuge bowl includes a plurality of truncated cones which are arranged into a stacked array and are closely spaced so as to enhance the separation efficiency. The incoming liquid flow exits the center tube through a pair of oil inlets and from there is directed into the stacked array of cones. In one embodiment, a top plate in conjunction with ribs on the inside surface of the centrifuge bowl accelerate and direct this flow into the upper portion of the stacked array. In another embodiment the stacked array is arranged as part of a disposable subassembly. In each embodiment, as the flow passes through the channels created between adjacent cones, particle separation occurs as the liquid continues to flow downwardly to the tangential flow nozzles.
U.S. Pat. No. 6,017,300, which issued Jan. 25, 2000 to Herman discloses a cone-stack centrifuge for separating particulate matter out of a circulating liquid. The construction of this centrifuge includes a cone-stack assembly which is configured with a hollow rotor hub and is constructed to rotate about an axis. The cone-stack assembly is mounted onto a shaft center tube which is attached to a hollow base hub of a base assembly. The base assembly further includes a liquid inlet, a first passageway, and a second passageway which is connected to the first passageway. The liquid inlet is connected to the hollow base hub by the first passageway. A bearing arrangement is positioned between the rotor hub and the shaft center tube for rotary motion of the cone-stack assembly. An impulse-turbine wheel is attached to the rotor hub and a flow jet nozzle is positioned so as to be directed at the turbine wheel. The flow jet nozzle is coupled to the second passageway for directing a flow jet of liquid at the turbine wheel in order to impart rotary motion to the cone-stack assembly. The liquid for the flow jet nozzle enters the cone-stack centrifuge by way of the liquid inlet. The same liquid inlet also provides the liquid which is circulated through the cone-stack assembly.
U.S. Pat. No. 6,019,717, which issued Feb. 1, 2000 to Herman is a continuation-in-part patent based upon U.S. Pat. No. 6,017,300. The U.S. Pat. No. 6,019,717 discloses a construction which is similar to the construction of the parent patent, but which includes the addition of a honeycomb-like insert which is assembled into the flow jet nozzle in order to reduce inlet turbulence and improve the turbine efficiency.
The increased separation efficiency provided by the inventions of the U.S. Pat. Nos. 5,575,912; 5,637,217; 6,017,300; and 6,019,717 is attributed in part to reduced sedimentation distance across the cone-to-cone gap. During the conception of the present invention, it was theoretically concluded that an equivalent effect could be achieved by converting the cone-stack subassembly into a radiating series of spiral vanes or plates with a constant axial cross-section geometry. The spiral vanes of the present invention, as described in some of the invention embodiments which will be described in greater detail, are integrally joined to a central hub and a top plate. In another related embodiment, the spiral vanes are also integrally joined to the liner shell as a unitary component. The preferred embodiment describes these combinations of component parts as a unitary and molded combination such that there is a single component. The top plate works in conjunction with acceleration vanes on the inner surface of the shell so as to route the exiting flow from the center portion of the centrifuge to the outer peripheral edge portion of the top plate where flow inlet holes are located. A divider shield located adjacent the outer periphery of the top plate functions to prevent the flow from diverting or bypassing the inlet holes and thereafter enter the spiral vane module through the outside perimeter between the vane gaps. If the flow was permitted to travel in this fashion, it could cause turbulence and some particle re-entrainment, since particles are being ejected in this zone. In the configuration of each spiral vane of certain embodiments, the outer peripheral edge is formed with a turbulence shield which extends the full axial length of each spiral vane as a means to further reduce fluid interaction between the outer quiescent sludge collection zone and the gap between adjacent spiral vanes where liquid flow and particle separation are occurring. Following the theoretical conception of this embodiment, an actual reduction to practice occurred. Initial testing was conducted in order to confirm the benefits and improvements offered by this first embodiment. In another embodiment of the present invention where the spiral vanes are made integral with the liner shell, it has been learned that other improvements are possible. For example, whenever there is an annular clearance space of some measurable size, between the inside surface of the liner shell or rotor shell and the outer edges of either a cone stack or spiral vane module, a xe2x80x9csludge zonexe2x80x9d is created. When this annular clearance space or sludge zone is free from any intruding objects, it will be disturbed by unhindered tangential and axial motion of the fluid, even during steady state operating conditions. These secondary flows cause separated sludge and particulate to become re-entrained, resulting in reduced separation performance. By extending the vanes to a point of contact with the liner shell or at least to a point of near abutment, the flow is limited into axial channels and this prevents any tangential motion of fluid relative to the rotors rotation. Less re-entrained sludge and particulate contributes to improved performance.
The commercial embodiments of the inventions disclosed in the U.S. Pat. Nos. 5,575,912; 5,637,217; 6,017,300; and 6,019,717 use a cone-stack subassembly which includes a stack of between twenty and fifty individual cones which must be separately molded, stacked, and aligned before assembly with the liner shell and base plate or, in the case of a disposable rotor design, with the hub or spool portion. This specific configuration results in higher tooling costs due to the need for large multi-cavity molds and higher assembly costs because of the time required to separately stack and align each of the individual cones. The xe2x80x9cunitary molded spiralxe2x80x9d concept of the present invention enables the replacement of all of the individual cones of the prior art with one molded component. The spiral vanes which comprise the unitary module can be simultaneously injection molded together with the hub portion for the module and the referenced top plate. Alternatively, these individual spiral vanes can be extruded with the hub and then assembled to a separately molded top plate. Even in this alternative approach to the manufacturing method of the present invention, the overall part count would be reduced from between twenty and fifty separate pieces to two pieces.
The present invention provides an alternative design to the aforementioned cone-stack technology. The design novelty and performance benefits of the self-driven, cone-stack designs as disclosed in U.S. Pat. Nos. 5,575,912; 5,637,217; 6,017,300; and 6,019,717 have been demonstrated in actual use. While some of the xe2x80x9ckeysxe2x80x9d to the success of these earlier inventions have been retained in the present invention, namely the self-driven concept and the reduced sedimentation distance across the inter-cone gaps, the basic design has changed. The replacement of the vertical stack of individually molded cones with a single spiral vane module is a significant structural change and is believed to represent a novel and unobvious advance in the art.
One embodiment of the present invention concerns a centrifuge that includes a base plate and rotor shell. The base plate has a center tube extending therefrom along a longitudinal axis. The center tube is constructed and arranged to deliver fluid. The rotor shell defines an inner cavity and the shell has a plurality of spiral vanes extending along the longitudinal axis within the inner cavity and extending spirally around the center tube. The vanes are integrally formed with the rotor shell.
A further form concerns a rotor shell for a centrifuge. The rotor shell includes an outer shell portion that has an annular engagement edge constructed and arranged to engage a lower shell portion. The outer shell portion defines an inner cavity, and the outer shell has a longitudinal axis. A plurality of spiral vanes are integrally formed within the outer shell. The spiral vanes extend spirally in the inner cavity and extend along the longitudinal axis.
Another form of the present invention concerns a method of manufacturing a centrifuge. A rotor shell is molded with a plurality of spiral vanes integrally formed with the rotor shell. The rotor shell defines an inner cavity and the spiral vanes extend spirally in the inner cavity. The spiral vanes have an inner edge that define a center tube passage. A base plate with a center tube is provided and the center tube is inserted into the center tube passage.
One object of the present invention is to provide an improved self-driven centrifuge which includes a separation vane module
Related objects and advantages of the present invention will be apparent from the following description.